Composite polybasic salt, process for producing the same, and use

ABSTRACT

A composite metal polybasic salt containing a trivalent metal and magnesium as metal components and having a novel crystal structure, and a method of preparing the same. The invention further deals with a composite metal polybasic salt which has anion-exchanging property, which by itself is useful as an anion-exchanger, capable of introducing anions suited for the use upon anion-exchange, and finds a wide range of applications, and a method of preparing the same. The composite metal polybasic salt has a particular chemical composition and X-ray diffraction peaks, and further has a degree of orientation (I o ) of not smaller than 1.5.

TECHNICAL FIELD

The present invention relates to a composite metal polybasic salt havinga novel crystalline structure, a method of preparing the same and usethereof.

BACKGROUND ART

As synthetic composite metal hydroxides, there have heretofore beenknown a hydrotalcite-type synthetic mineral (e.g., Japanese ExaminedPatent Publication (Kokoku) No. 32198/1972) and a salt of lithiumaluminum composite hydroxide (e.g., Japanese Examined Patent Publication(Kokoku) No. 2858/1995).

There has further been known a polybasic aluminum-magnesium salt.Japanese Examined Patent Publication (Kokoku) No. 38997/1974 teaches amethod of producing a polybasic aluminum salt by reacting a polybasicaluminum sulfate with a magnesium hydroxide at a molar ratio ofAl/Mg=1/2 to 4/3 in the presence of water. There has been further statedthat the polybasic aluminum magnesium salt can be effectively used as anantacid.

Japanese Unexamined Patent Publication (Kokai) No. 204617/1985 teaches amethod of preparing a magaldrate expressed by the formulaAl₅Mg₁₀(OH)₃₁(SO₄)₂.xH₂O by reacting an active aluminum hydroxide with astoichiometric amount of water-soluble sulfate-containing compound,active magnesium oxide and(or) magnesium hydroxide in the presence ofwater and, if necessary, drying the resulting magaldrate paste.

Japanese Unexamined Patent Publication (Kokai) No. 102085/1989 disclosesa novel aluminum magnesium hydroxy compound represented by the formulaAlxMgy(OH)_(35−z)R₂.nH₂O [wherein R is a residue RC00- of monocarboxylicacid, and indexes x, y and z satisfy the following conditions 3≦x ≦9,4≦y≦13, 3≦z≦5 and 3x+2y=35].

Japanese Unexamined Patent Publication (Kokai) No. 164432/1989 disclosesan aluminum magnesium hydroxy compound having a layer structurerepresented by the general formula AlxMgy(OH)_(35−z)R₂.nH₂O [wherein Ris a residue RC00- of monocarboxylic acid, RC00- having 2 to 22 carbonatoms, and indexes x, y and z satisfy the following conditions 3≦x≦9,4≦y≦13, 3≦z≦5 and 3x+2y=35], and a gel composition containing anoleophilic organic compound which is in the liquid form at roomtemperature (20° C.).

Japanese Examined Patent Publication (Kokoku) No. 59977/1989 discloses acrystalline basic aluminum magnesium carbonate represented by theformula Al₂Mg₆(OH)₁₂(CO₃)₂.xH₂O [wherein x≦4].

Further, Japanese Examined Patent Publication (Kokoku) No. 52409/1991discloses a method of producing a hydroxyaluminum magnesium sulfate byreacting a solid magnesium hydroxide and/or magnesium oxide with anaqueous solution of aluminum sulfate at an atomic ratio ofmagnesium:aluminum of from 1:1 to 3:1 until the pH of the reactionmixture becomes 4.0 to 8.0, removing the water-soluble component fromthe reaction mixture by a known method, followed, if necessary, bydrying.

A conventional polybasic aluminum magnesium salt, e.g., a USP-referredstandard magaldrate exhibits diffraction peaks at 2θ=10 to 12°, 2θ=22 to24°, 2θ=33 to 35°, 2θ=45 to 47° and 2θ=60 to 63° in the X-raydiffraction (Cu-α), whereas the polybasic aluminum magnesium salt of thepresent invention in which the anions are sulfuric ions exhibitsdiffraction peaks at 2θ=2 to 15°, 2θ=19.5 to 24° and 2θ=33 to 50° in theX-ray diffraction (Cu-α), and a single peak at 2θ=60 to 64°. The presentinventors have succeeded in synthesizing a novel composite metalpolybasic salt that has an explicit crystal structure exhibiting asingle X-ray diffraction (Cu-α) peak at 2θ=33 to 50°, the crystalstructure being different from those of hydrotalcites.

The inventors have further discovered that the composite metal polybasicsalt can be effectively used as an additive for resins, as a heatinsulator and as an anion-exchanger.

DISCLOSURE OF THE INVENTION

The object of the present invention is to provide a composite metalpolybasic salt containing a trivalent metal and magnesium as metalcomponents and having a novel crystal structure, and a method ofpreparing the same.

Another object of the present invention is to provide a composite metalpolybasic salt which has anion-exchanging property, which by itself isuseful as an anion-exchanger, capable of introducing anions suited forthe use upon anion-exchange, and finds a wide range of applications, anda method of preparing the same.

According to the present invention, there is provided a composite metalpolybasic salt having a chemical composition represented by thefollowing general formula (1),

M³⁺ _(p)Mg_(q)(OH)_(y)(A)_(z) .nH₂O  (1)

wherein M³⁺ is a trivalent metal, A is an inorganic or organic anion,and p, q, y and z are numbers satisfying the following formulas,

(i) 3p+2q−y−mz=0 (wherein m is a valency of anion A),

(ii) 0.3≦q/p≦2.5,

(iii) 1.5≦y/(p+q)≦3.0, and

(iv) 4.0≦(p+q)/z≦20.0, and

n is a number of not larger than 7, exhibiting diffraction peaks at 2θ=2to 15°, 2θ=19.5 to 24°and 2θ=33 to 50°, and a single peak at 2θ=60 to64° in the X-ray diffraction (Cu-α), and having a degree of orientation(I₀) represented by the following formula (2) of not smaller than 1.5,

I ₀ =I ₁₀ /I ₆₀  (2)

wherein I₁₀ is an X-ray diffraction peak intensity at 2θ=2 to 15°, andI₆₀ is an X-ray diffraction peak intensity at 2θ=60 to 64°.

In the present invention, it is desired that an X-ray diffraction (Cu-α)peak at 2θ=33 to 50° is a single peak.

In the present invention, it is desired that the trivalent metal (M³⁺)in the above formula is aluminum. In this case, q/p can be not largerthan 2.0.

In the present invention, further, it is desired that the anions (A) inthe above formula are sulfuric acid ions. The sulfuric acid ions haveanion-exchanging property, and can be exchanged with carbonic acid ions,organocarboxylic acid ions, phosphoric acid ions, silicic acid ions,perchloric acid ions, aluminic acid ions or sulfonic acid ions.

The composite metal polybasic salt of the present invention exhibitsX-ray diffraction peaks at the above-mentioned Bragg angle. For example,the Al—Mg—SO₄ composite metal polybasic salt which is a product of theinvention, generally, has the following X-ray diffraction image:

2 θ Relative intensity 10 to 12° 100% 20 to 22° 20 to 80% 33 to 50° 10to 60% 60 to 63°  5 to 50%

In this case, the degree of orientation (I₀) is from 2 to 20.

When photographed by using a scanning-type electron microscope, thecomposite metal polybasic salt of the present invention has a pleat-likethin-piece texture with a honeycomb-type or pumice-type internalstructure.

Among the above X-ray diffraction peaks, a peak at 2θ=33 to 50° issingular, and a laminate asymmetric index (Is) defined by the followingformula (3),

Is=tan θ₂/tan θ₁  (3)

wherein θ₁ is an angle subtended by a peak perpendicular in the X-raydiffraction peak of a predetermined spacing and a peak tangent on thenarrow angle side, and θ₂ is an angle subtended by the peakperpendicular at the above peak and a peak tangent on the wide angleside, is not smaller than 1.5 at a peak of 2θ=33 to 50°.

According to the present invention, there is further provided a methodof preparing a composite metal polybasic salt by reacting awater-soluble salt of a trivalent metal with an oxide, a hydroxide or awater-soluble salt of magnesium under the conditions of a pH of from 6.0to 9.0 and a temperature of not lower than 50° C. and, preferably, notlower than 80° C. and, if necessary, executing the ion exchange in thepresence of an acid or a soluble salt of acid.

According to the present invention, further, there is provided anadditive for resins, a heat insulator and an anion-exchanger comprisingthe composite metal polybasic salt.

In the anion-exchanger, it is desired that the anions of the compositemetal polybasic salt are sulfuric acid ions.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram comparing infrared-ray absorption spectra ofcomposite metal polybasic salts which are the products of the inventionwith that of a hydrotalcite;

FIG. 2 is a diagram illustrating an X-ray diffraction image of anAl—Mg-type composite metal polybasic salt of the present invention;

FIG. 3 is a diagram illustrating an X-ray diffraction image of a knownmagaldrate;

FIG. 4 is a diagram illustrating an X-ray diffraction image of a USPstandard magaldrate;

FIG. 5 is a diagram illustrating an X-ray diffraction image of thehydrotalcite;

FIG. 6 is a diagram illustrating an X-ray diffraction image of a salt oflithium aluminum composite hydroxide;

FIG. 7 is a diagram illustrating how to find a laminate asymmetricindex;

FIG. 8 is a diagram illustrating the results of differential thermalanalysis of the composite metal polybasic salt which is a product of thepresent invention;

FIG. 9 is a scanning-type electron microphotograph showing the granularstructure of the Al—Mg-type composite metal polybasic salt in which theanions are sulfuric acid ions;

FIG. 10 is a scanning-type electron microphotograph showing the granularstructure of the Al—Mg-type composite metal polybasic salt in which theanions are stearic acid ions;

FIG. 11 is a diagram illustrating a relationship between the feedingmolar ratio of Mg/M³⁺ in the starting materials and the molar ratio ofMg/M³⁺ in the product in relation to the Al—Mg-type composite metalpolybasic salt which is the product of the present invention;

FIG. 12 is a diagram illustrating an increase in the molar ratio ofSO₃/Al in the product accompanying an increase in the molar ratio ofMg/Al in relation to the Al—Mg-type composite metal polybasic salt whichis the product of the present invention; and

FIG. 13 is a diagram illustrating X-ray diffraction images of a productof when the feeding molar ratio Mg/Al of starting materials is changedin relation to the Al—Mg composite metal polybasic salt which is theproduct of the present invention.

EMBODIMENT OF THE INVENTION

[Composite Metal Polybasic Salt]

A first feature of the composite metal polybasic salt (hereinafter oftenreferred to as PBS) of the present invention is that it has a chemicalcomposition expressed by the above-mentioned formula (1). That is, thenumber p of mols of the trivalent metal, the number q of mols ofmagnesium metal, the number y of mols of hydroxyl groups and the numberz of mols of anions all lie within ranges satisfying the above formulas(i) to (iv).

A hydrotalcite which is a representative example of the known compositemetal polybasic salt or of the composite metal hydroxide salt,typically, has a chemical composition expressed by the following formula(4),

Mg₆Al₂(OH)₁₆CO₃ .nH₂O  (4)

and q/p in the above-mentioned formula (ii) corresponds to 3.0. In thecomposite metal polybasic salt of the present invention, however, q/p isnot larger than 2.5 and, particularly, not larger than 2.0, and has achemical composition different from that of the hydrotalcite.

The magaldrate, Al₅Mg₁₀(OH)₃₁(SO₄)₂.xH₂O, which is a known polybasicsalt exhibits X-ray diffraction (Cu-α) peaks at 2θ=10 to 12°, 2θ=22 to24°, 2θ=33 to 35°, 2θ=38 to 40°, 2θ=45 to 47°, and 2θ=60 to 63°, and hasa laminate asymmetric index (Is) defined by the following formula (3),

Is=tan θ₂/tan θ₁  (3)

wherein θ₁ is an angle subtended by a peak perpendicular in the X-raydiffraction peak of a predetermined spacing and a peak tangent on thenarrow angle side, and θ₂ is an angle subtended by the peakperpendicular at the above peak and a peak tangent on the wide angleside, over a range of from 1.0 to 2.5 at a peak of 2θ=33 to 35°, andfurther has a degree of orientation (I₀) represented by the followingformula (2),

I ₀ =I ₁₀ /I ₆₀  (2)

wherein I₁₀ is an X-ray diffraction peak intensity at 2θ=2 to 15°, andI₆₀ is an X-ray diffraction peak intensity at 2θ=60 to 64°, of notlarger than 1. Accordingly, the magaldrate is different in a crystalstructure from the product of the present invention.

As another example of the composite metal polybasic salt, there has beenknown a salt of lithium aluminum composite hydroxide of the followingformula (5),

[Al₂Li(OH)₆ ]nX.mH₂O  (5)

This compound does not contain a divalent metal but has a monovalentmetal, making a difference from the composite metal polybasic salt ofthe present invention. Even if two mols of a monovalent metal isequivalent to a mol of a divalent metal, q/p in the above-mentionedformula ii) corresponds to 0.25 when X is CO₃ or SO₃ (n=2). In thecomposite metal polybasic salt of the present invention, q/p is notsmaller than 0.3 and its chemical composition is also different fromthat of the known salt of lithium aluminum composite hydroxide.

It is considered that the composite metal polybasic salt of the presentinvention has the following chemical structure. In this compound, aMg(OH)₆ octahedral layer of which Mg is isomorphous-substituted by M³⁺serves as a basic layer, and anions such as sulfuric acid radicals areincorporated among the basic layers in a form to be balanced with excessof cations due to the substitution. The layered crystal structure isformed by a stack of many basic structures.

Anions such as sulfuric acid radicals present in the composite metalpolybasic salt have anion-exchanging property and can be substitutedwith carbonic acid ions, organocarboxylic acid ions, phosphoric acidions, silicic acid ions (including condensed silicic acid ions), and thelike ions.

The content Qo (milliequivalent/100 g) of sulfuric acid radicals in thecomposite metal polybasic salt is from 240 to 420 milliequivalent/100 g.

As the trivalent metal M³⁺ constituting the composite metal polybasicsalt, there can be exemplified Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Y,Ru, Rh, In, Sb, La, Ce, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu,Os, Ir, Au, Bi, Ac and Th. Among them, Al is preferred.

As the anions A constituting the composite metal polybasic salt, therecan be exemplified inorganic anions and organic anions. As the inorganicanions, there can be exemplified oxygen acid anions such as of S, P, Al,Si, N, B, V, Mn, Mo, W, Cr, Te and Sn, as well as carbonic acid anions.

As the organic anions, there can be exemplified carboxylic acid anionssuch as of acetic acid, propionic acid, butyric acid, palmitic acid,stearic acid, myristic acid, oleic acid, linolic acid, adipic acid,fumaric acid, maleic acid, citric acid, tartaric acid, malic acid,cyclohexanecarboxylic acid, benzoic acid, salicylic acid, phthalic acidand terephthalic acid; sulfonic acid anions such as of methane sulfonicacid, toluene sulfonic acid, lignin sulfonic acid and dodecylbenzenesulfonic acid; aromatic primary amines such as sulfanilic acid, aniline,o-toluidine, m-toluidine, metanilic acid and benzylamine as well as ofhydrochloric acid, nitric acid, sulfuric acid, phosphoric acid,hydrobromic acid and hydrofluoric acid.

FIG. 1 in the accompanying drawings shows infrared-ray absorptionspectra of the composite metal polybasic salts of the present inventionin comparison with the infrared-ray absorption spectrum of ahydrotalcite.

That is, FIG. 1(A) is an infrared-ray absorption spectrum of anAl—Mg-type composite metal polybasic salt in which the anions aresulfuric acid ions, FIG. 1(B) is an infrared-ray absorption spectrum ofan Al—Mg-type composite metal polybasic salt in which the anions arecarbonic acid ions, FIG. 1(C) is an infrared-ray absorption spectrum ofan Al—Mg-type composite metal polybasic salt in which the anions aredihydrogen phosphoric acid ions, FIG. 1(D) is an infrared-ray absorptionspectrum of an Al—Mg-type composite metal polybasic salt in which theanions are monohydrogen phosphoric acid ions, FIG. 1(E) is aninfrared-ray absorption spectrum of an Al—Mg-type composite metalpolybasic salt in which the anions are phosphoric acid ions, FIG. 1(F)is an infrared-ray absorption spectrum of an Al—Mg-type composite metalpolybasic salt in which the anions are silicic acid ions, FIG. 1(G) isan infrared-ray absorption spectrum of an Al—Mg-type composite metalpolybasic salt in which the anions are stearic acid ions, and FIG. 1(H)is an infrared-ray absorption spectrum of a hydrotalcite in which theanions are carbonic acid ions.

From these infrared-ray absorption spectra, it is learned that thecomposite metal polybasic salts of the present invention exhibitcharacteristic absorptions due to the hydroxyl group at wave numbers offrom 3800 to 2700 cm⁻¹ and characteristic absorptions due to theincorporated anions at wave numbers of from 900 to 1500 cm⁻¹. Inparticular, the composite metal polybasic salts of the invention exhibitsharp absorption peaks in the far infrared regions of a wave number ofnot larger than 2000 cm⁻¹, and are useful as a heat insulator forabsorbing heat rays.

Further, the Al—Mg-type composite metal polybasic salt in which theanions are stearic acid ions, exhibits characteristic absorptions due tothe methylene group at wave numbers of from 3000 to 2800 cm⁻¹ andcharacteristic absorptions due to carboxylate ions at wave numbers offrom 1650 to 1500 cm⁻¹.

The composite metal polybasic salt (PBS) of the present invention has anovel crystal structure which is quite different from those of the knownmagaldrate, hydrotalcite and a salt of lithium aluminum compositehydroxide.

FIG. 2 in the attached drawings shows an X-ray diffraction image of thePBS of the Al—Mg type according to the present invention.

FIGS. 3 and 4 are diagrams of X-ray diffraction images of knownmagaldrates, FIG. 5 is a diagram of an X-ray diffraction image of ahydrotalcite, and FIG. 6 is a diagram of an X-ray diffraction image of asalt of lithium aluminum composite hydroxide.

The composite metal polybasic salt of the invention in which the anionsare sulfuric acid ions exhibits substantially four diffraction peaks inthe X-ray diffraction (Cu-α) at 2θ=10 to 12°, 2θ=20 to 22°, 2θ=30 to 50°and 2θ=60 to 64°, the peak at 2θ=60 to 64° being a single peak.

On the other hand, the hydrotalcite (FIG. 5) exhibits two diffractionpeaks in the range of 2θ=38 to 50°, and another two diffraction peaks inthe range of 2θ=60 to 63°. Thus, the above two compounds exhibit quitedifferent X-ray diffraction images.

Further, the known magaldrate exhibits diffraction peaks at 2θ=10 to12°, 2θ=22 to 24°, 2θ=33 to 35°, 2θ=38 to 40°, 2θ=45 to 47° and 2θ=60 to63°. Thus, the two compounds exhibit quite different X-ray diffractionimages.

Similar differences are also recognized even in the case of a salt oflithium aluminum composite hydroxide (FIG. 6).

From the diffraction peaks of the X-ray diffraction images of the plane(001) at 2θ=10 to 12° of the composite metal polybasic salt of theinvention and the magaldrate, further, it will be leaned that thecrystals of the composite metal polybasic salt of the present inventionare developing in the direction of the C-axis. Further, the compositemetal polybasic salt which is a product of the present invention has adegree of orientation (I₀) represented by the following formula (2),

I ₀ =I ₁₀ /I ₆₀  (2)

wherein I₁₀ is an X-ray diffraction peak intensity at 2θ=2 to 15°, andI₆₀ is an X-ray diffraction peak intensity at 2θ=60 to 64°, of largerthan 2, which is quite different from that of the known magaldrate(I₀<1). From this fact, the composite metal polybasic salt which is aproduct of the invention has primary particles that are expanding in thedirection of AB-axis in the basic layer. Accordingly, the product of thepresent invention disperses well in the resin making it possible tostrikingly improve transparency of the blended resin, chlorine-trappingproperty, resistance against acid and heat resistance.

As will be obvious from FIG. 7, further, the composite metal polybasicsalt of the present invention has a feature in the X-ray diffractivefine structure called laminate asymmetry.

That is, it is obvious that the diffraction peak at 2 θ=33 to 50°exhibited by the composite metal polybasic salt of the invention is anasymmetric peak.

In other words, it will be understood that the asymmetric peak risesrelatively sharply on the narrow angle side (side on where 2θ is small)and is mildly inclined on the wide angle side (side on where 2θ islarge). The asymmetric peak becomes conspicuous particularly at 2θ=33 to50°. Asymmetry similarly appears even at a peak of 2θ=60 to 64° thoughthe degree of asymmetry is small.

In this specification, the laminate asymmetric index (Is) is defined asdescribed below. That is, an X-ray diffraction chart shown in FIG. 7 isobtained by a method described in an Example appearing later. A maximuminclination peak tangent a on the narrow angle side and a maximuminclination peak tangent b on the broad angle side, are drawn on a peakat 2θ=33 to 50°, and a perpendicular c is drawn from a point where thetangent a intersects the tangent b. Next, an angle θ1 subtended by thetangent a and the perpendicular c, and an angle θ2 subtended by thetangent b and the perpendicular c, are found. The laminate asymmetricindex (Is) is found from these angles in compliance with the aboveformula (2).

The laminate asymmetric index (Is) is 1.0 when the peak is completelysymmetrical, and increases as the breaking angle becomes larger than therising angle. The laminate asymmetric index (Is) of the known magaldratecan similarly be found to be 1.36, and the diffraction peak at 2θ=33 to35° is a symmetrical peak.

The laminate asymmetric index (Is) has the following meaning. In waspointed out already that the PBS of the present invention has a laminarcrystal structure in which basic layers of M³⁺ _(p)Mg_(q)(OH)_(y) arestacked one upon the other. However, it is believed that the sizes(lengths and areas) of the basic layers are not uniform but are varyingover wide ranges and, besides, the basic layers are twisted or curvedforming a structure which is not plane.

In the PBS of the present invention, therefore, the anions easilyexchange ions offering a large ion-exchange capacity and a largeion-exchange rate. When this is used as an additive for a resin, fortrapping, for example, chlorine ions, then, an excellent ability isexhibited.

When heated from room temperature up to a temperature of 200° C., thecomposite metal polybasic salt of the present invention exhibits aweight reduction ratio of not larger than 15% by weight and,particularly, not larger than 5% by weight, and offers a distinguishedadvantage that it does not develop foaming at a resin-workingtemperature when it is mixed into the resin. The hydrotalcite has adefect of developing foaming as the water separates at the resin-workingtemperature. The composite metal polybasic salt of the present inventionis free from this problem.

FIG. 8 shows the results of differential thermal analysis (DTA) of thecomposite metal polybasic salt of the invention and of the hydrotalcite.The hydrotalcite exhibits a very large endothermic peak due to thevaporization of water in a temperature range of from 190 to 240° C.,whereas the PBS does not exhibit such a large endothermic peak provingits excellent resistance against the foaming.

The composite metal polybasic salt of the present invention varies thesurface area to a large extent depending upon the kind of anions to beexchanged, and possesses a relative specific surface area and a smallporous volume when the anions are sulfuric acid ions. In this case, thePBS of the present invention has a BET specific surface area of notlarger than 20 m²/g and, particularly, in a range of from 0.3 to 10m²/g, and a porous volume of those pores having diameters of from 17 to3000 angstroms as found by the CI method of from 0.0005 to 0.05 ml/gand, particularly, from 0.02 to 0.035 ml/g. When the anions are silicicacid ions, on the other hand, the PBS of the present invention has alarge specific surface area and a large porous volume. In the case ofExample 10, for example, the BET specific surface area is about 147 m²/gand the porous volume of those pores having diameters of from 17 to 3000angstroms is about 0.425 ml/g as found by the CI method.

The composite metal polybasic salt of the present invention has a volumebased median diameter (D₅₀) of, generally, from 0.1 to 20 μm and,particularly, from 2 to 10 μm as measured by the laser diffractionmethod.

FIG. 9 is a scanning-type electron microphotograph showing the granularstructure of an Al—Mg-type composite metal polybasic salt in which theanions are sulfuric acid ions, and FIG. 10 is a scanning-type electronmicrophotograph showing the granular structure of an Al—Mg-typecomposite metal polybasic salt in which the anions are stearic acidions.

These photographs tell an interesting fact that in the PBS of the Al—Mgtype, the primary particles have a honeycomb- or pumice-type internalstructure, and are agglomerated to form secondary particles.

The PBS of the present invention has a small porous volume as measuredabove despite of its honeycomb-type or pumice-type internal structurewith pleat-like thin-piece texture, probably because the holes that areformed have diameters considerably larger than the above-mentioned finepore diameters.

Further, comparison of FIG. 9 with FIG. 10 tells the fact that in thePBS of the stearic acid type, the primary particles are becomingconsiderably bulky due to the introduction of the stearic acid.

[Method of Preparation]

According to the present invention, the composite metal polybasic saltis prepared by reacting a water-soluble salt of a trivalent metal withan oxide, a hydroxide or a water-soluble salt of magnesium under theconditions of a pH of from 6.0 to 9.0 and a temperature of not lowerthan 50° C. and, preferably, not lower than 80° C. and, if necessary,executing the ion exchange in the presence of an acid or a soluble saltof acid.

As the water-soluble salt of a trivalent metal such as Al or the like,there can be used any one of a chloride, a nitrate or a sulfate that issoluble in water. From the standpoint of easy synthesis, however, it isdesired in the present invention to synthesize the composite metalpolybasic salt in the form of a sulfate. It is therefore most desired touse the composite metal polybasic salt in the form of a sulfate.

The starting divalent Mg metal can be used in any form of an oxide, ahydroxide or a water-soluble salt. From the standpoint of synthesis,however, it is most convenient to use an oxide such as magnesium oxideor a hydroxide such as magnesium hydroxide. Even when a water-solublesalt such as a chloride, a nitrate or a sulfate of a divalent metal isused, it is possible to synthesize a composite metal polybasic saltaccording to the present invention by controlling the pH in the controlsystem to lie within the above-mentioned range, as a matter of course.

In the present invention, it is important to carry out the reaction ofthe above-mentioned starting materials while maintaining the pH at thetime when the reaction is finished to lie within a range of from 6.0 to9.0 and, particularly, from 6.5 to 8.0, and maintaining the reactiontemperature to be not lower than 50° C. and, particularly, from 80 to180° C.

When the pH of the reaction system lies outside the above range, itbecomes difficult to form the composite metal polybasic salt. That is,the composite metal polybasic salt has a feature in that it possessesboth the hydroxyl group and the anionic group that are bonded to eachother. When the pH becomes larger than the above range, it becomesdifficult to introduce the anionic group. When the pH becomes smallerthan the above range, on the other hand, it becomes difficult tointroduce the hydroxyl group.

When the temperature becomes lower than the above-mentioned range, itbecomes difficult to synthesize the composite metal polybasic salt.

The reacting and mixing ratio of the trivalent metal compound and themagnesium metal compound is so set that the composition ratio of theabove-mentioned general formula (1) is satisfied. In general, the molarratio of Mg/M³⁺ in the product tends to become smaller than the feedingmolar ratio of Mg/M³⁺ in the starting material.

FIG. 11 in the accompanying drawing illustrates a relationship betweenthe feeding molar ratio of Mg/M³⁺ in the starting material and the molarratio of Mg/M³⁺ in the product in relation to the Al—Mg-type compositemetal polybasic salt. The relationship between the two is almost linear,from which it will be understood that the molar ratio of Mg/M³⁺ in thefinal product can be determined by determining the feeding molar ratio.

When Mg(OH)₂ is used as the starting Mg material and Al₂(SO₄)₃ is usedas a starting M³⁺ material, it is desired that the feeding molar ratioof Mg/M³⁺ is in a range of from 1.3 to 3.5 and, particularly, from 1.6to 3.1.

There also exists a predetermined relationship among the feeding molarratio of Mg/M³⁺ in the starting material, the molar ratio of Mg/M³⁺ inthe product and the molar ratio of A/M³⁺ in the product. In general, themolar ratio of A/M³⁺ in the product increases with an increase in themolar ratio of Mg/M³⁺.

FIG. 12 illustrates a relationship between the above two, from which itwill be learned that the molar ratio of SO₃/Al in the productmonotonously increases with a increase in the molar ratio of Mg/Al. Itwas pointed out already that in the PBS of the present invention, aMg(OH)₆ octahedral layer of which Mg is isomorphous-substituted by M³⁺serves as a basic layer, and anions such as sulfuric acid radicals areincorporated among the basic layers in a form to be balanced with excessof cations due to the substitution. When the sulfuric acid radicals areall incorporated in a form to be balanced by excess of cations, themolar ratio of SO₃/Al becomes 0.5. Therefore, the fact of FIG. 12 tellsthat in a state where the molar ratio of Al is small, nearly ideal stateholds. However, as the molar ratio of Al increases, the degree ofincorporation of the sulfuric acid radicals decreases and the bonds withthe hydroxyl groups increase.

FIG. 13 shows an X-ray diffraction image of a product of when thefeeding molar ratio Mg/Al of the starting material is changed inrelation to the Al—Mg composite metal polybasic salt. These results tellthat the crystal structure of the present invention is stably formedwhen the molar ratio of Mg/Al lies within a range of from 1.8 to 3.0.

In synthesizing the composite metal polybasic salt of the presentinvention, there is no particular limitation on the order of mixing thetwo starting materials. For example, a solution of an oxide of magnesiummetal, of a slurry of a hydroxide thereof or of water-soluble saltsthereof may be added to an aqueous solution of trivalent metal salts.Conversely, an aqueous solution of trivalent metal salts may be added toan aqueous solution of an oxide of a divalent metal, of a slurry of ahydroxide thereof or of water-soluble salts thereof, or they may besimultaneously added together.

The reaction can be completed by maintaining the reaction mixture at theabove-mentioned temperature for about 2 to 72 hours with stirring.Though not generally required, the reaction may be conducted under thehydrothermal conditions by using a pressurized container.

The reaction product is washed with water, subjected to the solid-liquidseparation operation such as filtration, dried at 60 to 150° C., and, ifnecessary, is heat-treated at 150 to 230° C. to obtain a product.

In the composite metal polybasic salt of the present invention, avariety of anions can be introduced by the ion-exchange method. As thestarting composite metal polybasic salt to be used for theanion-exchange, it is desired to use the composite metal polybasic saltof the sulfuric acid type.

As the anions to be subjected to the ion-exchange, there is used analkali metal salt such as sodium salts of the above-mentioned anions.For example, a sodium bicarbonate or a sodium carbonate is used forintroducing carboxylic acid radicals, a sodium carboxylate or sodiumsulfonate is used for introducing organic acid anions, a sodiumphosphate, a monohydrogen sodium phosphate or a dihydrogen sodiumphosphate is used for introducing phosphoric acid radicals, and a sodiumsilicate is used for introducing silicic acid radicals, to which only,however, the invention is in no way limited.

Anions based on the ion exchange can be introduced by bringing acomposite metal polybasic salt of the sulfuric acid type in the form ofa powder or a wet cake into uniform contact with an aqueous solution ofa salt of the above-mentioned anions at a temperature of from 0 to 100°C. In general, the ion-exchange processing is completed by executing thecontact for from about 5 minutes to about 3 hours.

The obtained product is subjected to the filtration, washing with water,drying and, if necessary, to the pulverization and classification toobtain a product.

The composite metal polybasic salt of the present invention can be usedin its own form as an additive for resins, as an anion-exchanger or as aheat insulator. If necessary, however, it may be coated with an organicassistant or an inorganic assistant and can, then, be used for a varietyof applications.

As the organic assistant, there can be exemplified such coating agentsas metal soaps such as calcium salt, zinc salt, magnesium salt andbarium salt of stearic acid, palmitic acid or lauric acid; silanecoupling agent, aluminum coupling agent, titanium coupling agent,zirconium coupling agent, various waxes, and unmodified or modifiedresins (e.g., rosin, petroleum resin, etc.). The composite metalpolybasic salt of the present invention can be treated for its surfaceswith the above coating agent and can be used for a variety ofapplications.

It is desired to use the coating agent in an amount of from 0.5 to 10%by weight and, particularly, from 1 to 5% by weight with respect to thePBS.

As the inorganic assistant, there can be exemplified regular particlesof fine particulate silica such as aerosil and hydrophobically treatedaerosil, silicates such as calcium silicate and magnesium silicate,metal oxides such as calcia, magnesia and titania, metal hydroxide suchas magnesium hydroxide and aluminum hydroxide, metal carbonates such ascalcium carbonate, synthetic zeolites of the A-type and P-type andacid-treated products thereof or metal ion-exchanged product thereof,with which the PBS can be blended or sprinkled.

It is desired to use these inorganic assistants in an amount of from0.01 to 200% by weight and, particularly, from 0.1 to 200% by weight perthe PBS.

As additives, there may be further blended urea, ethyleneurea,propyleneurea, 5-hydroxypropyleneurea, 5-methoxypropyleneurea,5-methylpropyleneurea, parabanic acid, 4,5-dimethoxyethyleneurea,pyrrolidene, piperidine, morpholine, dicyandiamide,2-hydrazobenzothiazole, potassium permanganate, benzalkonium chloride,iodophor, hydrazine, hydrazine sulfate, aluminum sulfate hydrazinesulfate complex salt, organic/inorganic antibacterial agent (iodophorand silver-exchanged zeolite), and optical catalyst (titanium oxide,etc.).

[Use]

The PBS of the present invention has excellent properties as describedabove. By utilizing these properties, the PBS can be used in suchapplications as an additive for resins, an ion (anion)-exchanger, a heatinsulator, a base member for cosmetics, a de-odoring/antibacterialagent, a flame retardant, an ultraviolet ray-absorbing agent, ananocomposite starting material, etc.

The composite metal polybasic salt of the present invention is useful asan additive for thermoplastic resins, thermosetting resins and variousrubbers.

That is, the composite metal polybasic salt of the present inventiondoes not develop foaming that is caused when the water separates at theresin-working temperature, can be easily blended in the resin, andexhibits excellent heat stability since it contains components such asmagnesium metal, trivalent metal components and hydroxyl groups thatimpart heat-stabilizing property to the resins. Besides, the compositemetal polybasic salt has anion-exchanging property and exhibitsexcellent property for trapping chlorine ions. Moreover, the compositemetal polybasic salt absorbs far infrared rays and exhibits excellentheat-retaining property.

Thus, the composite metal polybasic salt of the invention can be blendedin the resins as a heat stabilizer, a halogen catcher, a heat-retainingagent (a heat insulator) or as an anti-blocking agent.

As the thermoplastic resin to be blended with the composite metalpolybasic salt of the present invention, there can be preferablyexemplified an olefin resin and, particularly, a low-, an intermediate-or a high-density polyethylene, an isotactic polypropylene, asyndiotactic polypropylene, or a polypropylene polymer which is acopolymer thereof with an ethylene or an α-olefin, a linear low-densitypolyethylene, an ethylene/propylene copolymer, a polybutene-1, anethylene/butene-1 copolymer, a propylene/butene-1 copolymer, anethylene/propylene/butene-1 copolymer, an ethylene/vinyl acetatecopolymer, an ionically crosslinked olefin copolymer (ionomer), or anethylene/acrylic acid ester copolymer, which may be used in a singlekind or being blended in two or more kinds.

The additive for resins of the present invention can also be used forother known resin films, fibers and resin-molded articles, such aspolyamides like nylon 6, nylon 6-6, nylon 6-10, nylon 11 and nylon 12,thermoplastic polyesters such as polyethylene terephthalate andpolybutylene terephthalate, as well as polycarbonate, polysulfone, vinylchloride resin, vinylidene chloride resin and vinyl fluoride resin.

When used as an additive for resins, it is desired that the compositemetal polybasic salt is used in an amount of from 0.01 to 200 parts byweight and, particularly, in an amount of from 0.1 to 100 parts byweight per 100 parts by weight of the thermoplastic resin.

The thermoplastic resins, various rubbers and thermosetting resins canbe blended with the composite metal polybasic salt of the presentinvention as an additive for reforming the resins.

As the elastomer polymer for rubbers, there can be exemplified anitrile-butadiene rubber (NBR), a styrene-butadiene rubber (SBR), achloroprene rubber (CR), a polybutadiene (BR), a polyisoprene (IIPI), abutyl rubber, a natural rubber, an ethylene-propylene rubber (EPR), anethylene-propylene-diene rubber (EPDM), a polyurethane, a siliconerubber and an acrylic rubber. As the thermoplastic elastomer, there canbe exemplified a styrene-butadiene-stylene block copolymer, astyrene-isoprene-styrene block copolymer, a hydrogenatedstyrene-butadiene-styrene block copolymer, a hydrogenatedstyrene-isoprene-stylene block copolymer, a partially crosslinkedolefinic thermoplastic elastomer.

As the thermosetting resin, there can be exemplified aphenol-formaldehyde resin, a furan-formaldehyde resin, axylene-formaldehyde resin, a ketone-formaldehyde resin, aurea-formaldehyde resin, a melamine-formaldehyde resin, an alkyd resin,an unsaturated polyester resin, an epoxy resin, a bismaleimide resin, atriallylcyanulate resin, a thermosetting acrylic resin and a siliconeresin, which may be used in a combination of two or more kinds.

In this case, the composite metal polybasic salt of the presentinvention is used in an amount of from 0.01 to 200 parts by weight and,particularly, in an amount of from 0.1 to 100 parts by weight per 100parts by weight of the thermoplastic resin, thermosetting resin orelastomer.

EXAMPLES

The invention will now be described by way of Examples to which only,however, the invention is in no way limited. The testing was conductedin compliance with the following methods.

(1) X-ray Diffraction Measurement

Measured for Cu-Kα by using a RAD-IB system manufactured by Rigaku DenkiCo.

Target Cu Filter curved crystalline graph- monochrometer Detector SCVoltage  35 KV Current  15 mA Count full-scale 8000 cps Smoothing point 25 Scanning speed 2° /mm Step sampling 0.033° Slit DS1° RS 0.30 mm SS1°Irradiating angle 6°

(2) Infrared Ray Absorption Spectral Analysis

Measured by using an FT/IR-610 infrared absorption spectral analyzermanufactured by Nihon Bunko Co.

(3) Differential Thermal Analysis

Measured by using a TAS-100-TG8110 manufactured by Rigaku Co. under themeasuring conditions of using a standard substance α-Al₂O₃, raising thetemperature at a rate of 10° C./min. in the air at 20 to 320° C.

(4) Observation Using a Scanning-type Electron Microscope

Observed by using a scanning electron microscope, S-570, manufactured byHitachi, Ltd.

(5) Specific Surface Area/porous Volume

Measured with N₂ using ASAP-2010 manufactured by Shimazu Seisakusho Co.

(6) Average Particle Diameter

Measured by using LS-230 manufactured by Coulter Co.

Example 1

Ion-exchanged water was added to 94.57 g of a magnesium hydroxide(MgO=64.2%) so that the total amount was 400 ml, followed by stirringand dispersion to prepare an Mg(OH)₂ slurry.

400 Grams of an aluminum sulfate (Al₂O₃=7.68%, SO₃=18.1%) was introducedinto a 1000-ml beaker and to which the above Mg(OH)₂ slurry wasgradually added at room temperature with stirring, and the mixture wasmessed-up to 1500 ml. Thereafter, the temperature was elevated to 90° C.to conduct the reaction for 5 hours.

After the reaction, the reaction product was filtered, washed with 3000ml of hot water, dried at 110° C. and was pulverized to obtain a whitepowder.

The composition of the obtained fine powder was analyzed to be asfollows. Properties were as shown in Table 1.

Al_(1.00)Mg_(1.23)(OH)_(4.71)(SO₄)_(0.37).1.6H₂O 2 θ Relative intensity10.30° 100% 22.40°  55% 37.10°  40% 63.20°  27%

Example 2

Ion-exchanged water was added to 87.01 g of a magnesium hydroxide(MgO=64.2%) in a 1000-ml beaker so that the total amount was 400 ml,followed by stirring and dispersion to prepare an Mg(OH)₂ slurry.

400 Grams of an aluminum sulfate (Al₂O₃=7.68%, SO₃=18.1%) was graduallyadded the above Mg(OH)₂ slurry at room temperature with stirring, andthe mixture was messed-up to 900 ml. Thereafter, the temperature waselevated to 90° C. to conduct the reaction for 10 hours.

After the reaction, the reaction product was filtered, washed with 1800ml of hot water, dried at 110° C. and was pulverized to obtain a whitepowder.

The composition of the obtained fine powder was analyzed to be asfollows. Properties were as shown in Table 1.

Al_(1.00)Mg_(1.23)(OH)_(4.50)(SO₄)_(0.35).1.6H₂O 2 θ Relative intensity10.30° 100% 20.33°  54% 35.33° 19% 61.13° 24%

Example 3

Ion-exchanged water was added to 170.23 g of a magnesium hydroxide(MgO=64.2%) in a 2000-ml beaker so that the total amount was 750 ml,followed by stirring and dispersion to prepare an Mg(OH)₂ slurry.

720 Grams of an aluminum sulfate (Al₂O₃=7.68%, SO₃=18.1%) was graduallyadded the above Mg(OH)₂ slurry at room temperature with stirring, andthe mixture was messed-up to 1500 ml. Thereafter, the temperature waselevated to 90° C. to conduct the reaction for 15 hours.

After the reaction, the reaction product was filtered, washed with 3000ml of hot water, dried at 110° C. and was pulverized to obtain a whitepowder.

The composition of the obtained fine powder was analyzed to be asfollows. Properties were as shown in Table 1.

Al_(1.00)Mg_(1.29)(OH)_(4.81)(SO₄)_(0.39).1.5H₂O 2 θ Relative intensity10.17° 100% 20.21°  66% 35.85°  23% 61.33°  29%

The polybasic salt EX-3 possessed a BET specific surface area of 4.15m²/g and a porous volume of 0.032 cc/g. An X-ray diffraction image ofthe polybasic salt EX-3 is shown in FIG. 2 and a scanning electronmicrophotograph thereof is shown in FIG. 9.

Example 4

3.80 Grams of NaHCO₃ (purity, 99%) was introduced into a 500-ml beaker,and to which ion-exchanged water was added to prepare 100 ml of a NaHCO₃solution.

Separately, 10 g of the fine white powder obtained in Example 3 wasdispersed in 200 ml of ion-exchanged water, and to which the aboveNaHCO₃ solution was added. The mixture was heated at 90° C. and wasstirred for two hours. After the reaction, the reaction product wasfiltered, washed with hot water, dried at 110° C. for 12 hours and waspulverized to obtain a white powder.

The composition of the obtained fine powder was analyzed to be asfollows. Properties were as shown in Table 1.

Al_(1.00)Mg_(1.23)(OH)_(4.81)(SO₄)_(0.11)(CO₃)_(0.28).1.7H₂O 2 θRelative intensity 11.67° 100% 23.47°  33% 35.03°  31% 39.50°  12%46.67°  9% 61.27°  29%

Example 5

17.91 Grams of sodium stearate was added to 300 ml of ion-exchangedwater in a 500-ml beaker, and the mixture was heated at 80° C. and wasstirred to prepare a sodium stearate solution.

Separately, 87.01 g of magnesium hydroxide (MgO=64.2%) and ion-exchangedwater were added into a 1000-ml beaker so that the total amount was 400ml, followed by stirring and dispersion to prepare an Mg(OH)₂ slurry.400 Grams of an aluminum sulfate (Al₂O₃=7.68%, SO₃=18.1%) was graduallyadded to the above Mg(OH)₂ slurry at room temperature with stirring, andthe mixture was messed-up to 900 ml. Thereafter, the temperature waselevated to 90° C. to conduct the reaction for 10 hours. After thereaction, the reaction product was filtered, washed with 1800 ml of hotwater, dried at 110° C. and was pulverized to obtain a white powder. 10Grams of the fine white powder was dispersed in 200 ml of ion-exchangedwater, which was, then, added to the above sodium stearate solution. Themixture was then heated at 90° C. and was stirred for two hours. Afterthe reaction, the reaction product was filtered, washed with 1000 ml ofhot water, and was dried at 110° C. using a blower-drier overnight.

The composition of the obtained fine powder was analyzed to be asfollows. Properties were as shown in Table 1.

Al_(1.00)Mg_(1.10)(OH)_(4.50)(C₁₈H₃₅O₂)_(0.35).0.8H₂O 2 θ Relativeintensity  2.26°  23%  5.20°  53%  8.34°  12% 21.14° 100% 35.48°  13%61.46°  9%

Example 6

1.87 Grams of NaOH was dissolved in 300 ml of ion-exchanged water in a500-ml beaker. 12.74 Grams of stearic acid was added thereto, and themixture was heated at 80° C. and was stirred to prepare a sodiumstearate solution.

Separately, 33.33 g of the reaction product (solid content of 30%) afterwashed obtained in Example 3 was dispersed in 200 ml of ion-exchangedwater. The mixture was added to the above sodium stearate solution andwas heated at 90° C. and was stirred for two hours. After the reaction,the reaction product was filtered, washed with 1000 ml of hot water andwas dried at 110° C. using a blower-drier overnight.

The composition of the obtained fine powder was analyzed to be asfollows. Properties were as shown in Table 1.

Al_(1.00)Mg_(1.29)(OH)_(4.81)(C₁₈H₃₅O₂)_(0.39).0.7H₂O 2 θ Relativeintensity  2.26°  20%  5.03°  44%  8.17°  5% 21.27° 100% 35.43°  15%61.20°  12%

The results of differential thermal analysis (DTA) of the polybasic saltare shown in FIG. 8 and a scanning-type electron microphotograph thereofis shown in FIG. 10.

Example 7

10.9 Grams of Na₂HPO₄.12H₂O (purity of 99%) was introduced into a 500-mlbeaker, and to which ion-exchanged water was added to prepare 250 ml ofan Na₂HPO₄ solution.

10 Grams of the fine white powder obtained in Example 3 was added to theabove Na₂HPO₄ solution, and the mixture was messed-up to 300 ml and washeated at 90° C. and was stirred for two hours. After the reaction, thereaction product was filtered, washed with 1000 ml of hot water, driedat 110° C. for 12 hours and was pulverized to obtain a fine whitepowder. The composition of the obtained fine powder was analyzed to beas follows. Properties were as shown in Table 1.

Al_(1.00)Mg_(1.32)(OH)_(5.18)(HPO₄)_(0.23).1.7H₂O 2 θ Relative intensity11.27° 100% 21.98°  42% 35.85°  37% 61.70°  38%

Example 8

A white powder was obtained through the same operation as in Example 7but using 9.53 g of NaH₂PO₄.2H₂O (purity of 99%) instead ofNa₂HPO₄.12H₂O.

The composition of the obtained fine powder was analyzed to be asfollows. Properties were as shown in Table 1.

Al_(1.00)Mg_(1.25)(OH)_(5.14)(H₂PO₄)_(0.36).1.9H₂O 2 θ Relativeintensity 10.13°  75% 21.30° 100% 36.30°  38% 61.66°  51%

Example 9

A white powder was obtained through the same operation as in Example 7but using 7.74 g of Na₃PO₄.12H₂O (purity of 99%) instead ofNa₂HPO₄.12H₂O.

The composition of the obtained fine powder was analyzed to be asfollows. Properties were as shown in Table 1.

Al_(1.00)Mg_(1.30)(OH)_(4.81)(SO₄)_(0.06).(Si₃O₇)_(0.34).1.3H₂O 2 θRelative intensity 11.71° 100% 23.24°  34% 35.55°  32% 61.30°  33%

Example 10

25.0 Grams of a sodium silicate solution No. 3 (SiO₂=22.0%, Na₂O=7.08%)was introduced into a 500-ml beaker, and to which ion-exchanged waterwas added to prepare 200 ml of a sodium silicate aqueous solution.

Separately, 33.33 g of the reaction product (solid content of 30%) afterwashed obtained in Example 3 was dispersed in 100 ml of ion-exchangedwater. The mixture was added to the above sodium silicate solution andwas heated at 50° C. and was stirred for two hours. After the reaction,the reaction product was filtered, washed with hot water, dried at 110°C. for 12 hours and was pulverized to obtain a fine white powder.

The composition of the obtained fine powder was analyzed to be asfollows. Properties were as shown in Table 1.

Al_(1.00)Mg_(1.30)(OH)_(4.81)(SO₄)_(0.06)(Si₃O₇)_(0.34).1.3H₂O 2 θRelative intensity  8.03°  31% 14.57°  30% 22.60° 100% 35.53°  46%61.37°  50%

TABLE 1 Laminate Specific Average asymmetric Degree of surface Porousparticle indexes orientation area volume diameter Is Io (m²/g) (ml/g)(μm) q/p y/q + p p + q/z Example No. 1 2.53 3.68 1.07 0.0042 4.1 0.472.40 7.35 2 7.85 4.15 3.40 0.0231 6.0 1.82 2.04 6.41 3 5.51 3.42 4.150.0318 1.29 2.10 5.87 4 1.71 — 1.30 2.09 5.90 5 5.38 — 1.10 2.14 6.29 63.22 — 1.29 2.10 5.87 7 5.41 — 1.32 2.23 10.09  8 2.72 — 1.25 2.28 6.259 6.74 — 1.57 2.14 11.68  10  1.53 — 146 0.425 1.30 2.09 5.75Comparative Example No. 1 1.36 0.57 — — — 2 — — 3 — — 0.25 2.00 p, q, yand z are indexes of M³⁺ _(p)Mg_(q)(OH)_(y)(A)_(z).nH₂O.

Comparative Example 1

Synthesis of Magaldrate

100.34 Grams of an aluminum sulfate (Al₂O₃=7.68%, SO₃=18.1%) was addedto 1112.4 g of an activated aluminum hydroxide paste (Al₂O₃=1.50%), andto which was further added 60.00 g of magnesium hydroxide (MgO=64.2%)with vigorous stirring. And then, the reaction mixture is left quietlyfor 24 hours to maintain the reaction.

The paste after the reaction was dried at 110° C. and was pulverized toobtain a white powder.

From the X-ray analysis, the obtained fine powder was a mixture of amagaldrate disclosed in Japanese Examined Patent Publication (Kokoku)No. 58210/1990 and an aluminum hydroxide (gibbsite), and the magaldrateonly could not be obtained.

FIG. 3 shows an X-ray diffraction image of the magaldrate disclosed inJapanese Examined Patent Publication (Kokoku) No. 58210/1990 and FIG. 4shows an X-ray diffraction image of a USP-referred standard magaldrate.Since these drawings do not show a scale of angles, the angles refer tovalues of the Journal of Pharmaceutical Science, Vol. 1.6, p. 325, 1978.

2 θ Relative intensity 11.42°  57% 23.22°  44% 34.91°  78% 39.16°  30%46.07°  37% 60.95° 100% 62.32°  85%

Comparative Example 2

Synthesis of Hydrotalcite

Ion-exchanged water was added to 121.21 g of Mg(OH)₂ (MgO=64.2%), 76.06g of Al(OH)₃ (purity of 99%) and 103.35 g of Na₂CO₃ (purity of 99%) suchthat the total amount was 4000 ml. The mixture was stirred to prepare aslurry which was then hydrothermally reacted at 170° C. for 24 hours.

After the reaction, the reaction product was filtered, washed with 6000ml of hot water, dried at 110° C. and was pulverized to obtain a whitepowder.

The composition of the obtained fine powder was analyzed to be asfollows.

Al₆Mg₂(OH)₁₆(CO₃).nH₂O 2 θ Relative intensity 11.63° 100% 23.38°  42%34.79°  21% 39.35°  16% 46.81°  17% 60.59°  6% 61.96°  7%

An X-ray diffraction image of the hydrotalcite is shown in FIG. 5.

Comparative Example 3

Synthesis of a Salt of Lithium Aluminum Composite Hydroxide.

25.00 Grams of sodium hydroxide (NaOH content of 96%) and 7.44 g ofsodium carbonate (Na₂CO₃ content of 99.7%) were added to 2 liters ofdistilled water with stirring, and the mixture was heated at 40° C.Then, to this solution was gradually added an aqueous solution which wasobtained by adding 4.33 g of lithium chloride (52.90% of Li₂O) and 49.78g of aluminum chloride (20.48% of Al₂O₃) to 500 ml of distilled watersuch that the molar ratio of Al/Li was 2.0. The reaction was conductedwith stirring at a temperature of 90° C. for 20 hours. The obtainedreaction suspension was filtered, washed with water, dried at 70° C. andwas, then, pulverized using a small sample mill to obtain a whitepowder.

The composition of the obtained fine powder was analyzed to be asfollows.

Li₂Al₄(OH)₁₂CO₃.nH₂O 2 θ Relative intensity 11.77° 100% 20.20°  11%23.61°  59% 36.07°  29% 40.63°  14% 48.03°  18% 63.24°  11% 64.54°  9%

An X-ray diffraction image of the salt of lithium aluminum compositehydroxide is shown in FIG. 6.

The present invention provides a composite metal polybasic saltcontaining a trivalent metal and magnesium as metal components andhaving a novel crystal structure, and a method of preparing the same.The invention further provides a composite metal polybasic salt whichhas anion-exchanging property, which by itself is useful as ananion-exchanger, capable of introducing anions suited for the use uponanion-exchange, and finds a wide range of applications, and a method ofpreparing the same.

What is claimed is:
 1. A composite metal polybasic salt having achemical composition represented by the following general formula (1),M³⁺ _(p)Mg_(q)(OH)_(y)(A)_(z).nH₂O  (1) wherein M³⁺ is Al, A is SO₄ ²⁻,and p, q, y, and z are numbers satisfying the following formulas,3p+2q−y−mz=0 (wherein m is a valency of anion A), 0.3≦q/p≦2.5,1.5≦y/(p+q)≦3.0, and 4.0≦(p+q)/z≦20.0, and n is a number of not largerthan 7, exhibiting diffraction peaks at 2θ=2 to 15° and 2θ=19.5 to 24°and a single peak at 2θ=33 to 50° and 2θ=60 to 64° in the X-raydiffraction (Cu-α), and having a degree of orientation (I₀) representedby the following formula (2) of not smaller than 1.5, I ₀ =I ₁₀ /I₆₀  (2) wherein I₁₀ is an X-ray diffraction peak intensity at 2θ=2 to15°, and I₆₀ is an X-ray diffraction peak intensity at 2θ=60 to 64°. 2.A composite metal polybasic salt according to claim 1, wherein an X-raydiffraction (Cu-α) peak at 2θ=10 to 12° has a relative intensity of100%, at 2θ=20 to 22° has a relative intensity of 20 to 80%, at 2θ=33 to50° has a relative intensity of 10 to 60% and at 2θ=60 to 63° has arelative intensity of 5 to 50%.
 3. A composite metal polybasic saltaccording to claim 1, wherein, when photographed by using ascanning-type electron microscope, said composite metal polybasic salthas a pleat-like thin-piece texture.
 4. A composite metal polybasic saltaccording to claim 1, wherein said composite metal polybasic salt has alaminate asymmetric index (Is) defined by the following formula (3),Is=tan θ₂/tan θ₁  (3) wherein θ₁ is an angle subtended by a peakperpendicular in the X-ray diffraction peak of a predetermined spacingand a peak tangent on the narrow angle side, and θ₂ is an anglesubtended by the peak perpendicular at the above peak and a peak tangenton the wide angle side, is not smaller than 1.5 at a peak of 2θ=33 to50°.
 5. An additive for resins comprising a composite metal polybasicsalt according to claim
 1. 6. A heat insulator comprising a compositemetal polybasic salt according to claim
 1. 7. An anion-exchangercomprising a composite metal polybasic salt according to claim 1.